Izaya Numata is an assistant research professor at GSCE. His research interests are in monitoring, characterizing and evaluating land-cover and land-use (LCLU) dynamics and human-environmental interactions that cause LCLU change. His primary concern is to understand interchangeable relationships between human activity and the environment that drive LCLU change. His research approach includes intensive use of remote sensing for biophysical and chemical characterization of land surfaces (land covers and land uses), monitoring its change, and the integration of different sources of data through GIS for the analysis of processes and consequences of LCLU change at different spatial and temporal scales. His research includes characterization/monitoring of forest degradation (deforestation, forest fire, logging and forest fragmentation), pasture degradation and carbon dynamics associated with human and climate impacts. His current research project focuses on vulnerability and responses of fragmented forests in southern Amazonia.

Research Projects

Vulnerability and Responses of Forest Edges to Drought in Amazonia

Recent severe droughts in Amazonia (2005 and 2010) have led to extensive damages to forest canopies and increased rate of tree mortality. After the 2005 drought, considered a once in century extreme event, the Amazon forest experienced another even more severe and extensive drought in 2010, with more than 600,000 km2 of forest area affected by both droughts. In addition to drought, the Amazon forest has been disturbed by deforestation over the past decades, and remnant forests are continuously fragmented into smaller habitats. Fragmented forests suffer several biological and ecological changes due to edge effects, including desiccation, that exacerbate regional forest degradation. As of 2010, 34% of the remaining forest outside protected areas is within 1 km of forest edges in the Amazon Basin, but much larger proportions are found in highly fragmented regions such as Rondônia (> 90%). Drought impacts should be larger and more severe in fragmented forest landscapes, especially within forest edges that dry more rapidly and intensely, however, the spatial scale of this phenomenon has not yet been quantified. As more frequent and intense extreme drought events are predicted in the future, more severe and extensive damages in regional ecosystems are expected as the remnant forests become increasingly fragmented with future land cover change in the Amazon. In this context, forest edges may serve as early warning indicators of potential tipping points at which climate change-triggered drought conditions could cause serious ecological changes to Amazonian ecosystems.

This proposal addresses “Vulnerability and responses of terrestrial ecosystems”, one of the research topics solicited by the 2013 NASA Terrestrial Ecology Program. We propose to investigate the vulnerability and responses of forest edges to drought in the southern Brazilian Amazon that was most severely affected by the recent droughts. Our approach is the following: 1) determine drought intensity and forest fragmentation metrics (landscape metrics) across the southern Brazilian Amazon (1998-2014); 2) conduct field studies of forest edges determined by drought intensity and forest fragmentation to examine vulnerability and responses of forest edges; 3) generate time series data of ET and vegetation indices from Landsat to assess regional canopy desiccation and its recovery from drought impacts; and 4) predict the future vulnerability of forest edges to drought based upon simulated future climate and land cover change scenarios.